The invention relates to a pump intended for oil spill recovery to pump oil or the like. The pump is suitable for installation in a small space in a collection apparatus. The problem with marketing small-scale oil collection apparatuses is that the available fixedly installable pumps which meet the requirements are size-wise unsuitable and very expensive in relation to the price of the actual apparatus. This is why oil transfer from small collection apparatuses is usually done using a low-pressure system located on the shore or onboard a vessel. A general problem with low-pressure systems is that when the oil is heavy, low-pressure is not necessarily enough to transfer it from the collector to the recovery container, but an apparatus using thrust pressure is required. For this purpose, it is necessary to have a pump which is light-weight, suitable in size, does not affect the buoyancy of the collection apparatus is inexpensive and pumps even the heavier oils as required.
It is an object of the invention to provide a piston pump which meets the set requirements. The pump body can be a pipe or the like. The body comprises an oil inlet and an oil outlet. Inside the body, two reciprocally working pistons, an extrusion piston and a suspended piston, are installed to produce together a smooth and efficient pumping motion for oil transfer. Between an eccentric run by a motor and the extrusion piston, there is an arm which produces the reciprocating motion of the extrusion piston. Inside the suspended piston, there is a spring bushing which guides a spring and keeps it in place when the piston moves. The suspended piston also works as a back-pressure valve of the pump. An end flange has a corresponding pin which acts as a support to the spring when it compresses. The extrusion piston has a closing clip for closing and opening the inlet. In the top part of the body, in connection with the inlet, there is an oil outlet recess which prevents the oil in front of the clip from being compressed and thus aids the oil in front of the clip to transfer back to the inlet. Between the suspended piston and the end flange, there is a spring which acts as a pressure equalizer of the pump and thus obtains from the suspended piston the counter-force which returns the suspended piston to its starting position when the oil chamber is empty. The pump works in such. a manner that the oil collected in the collection apparatus first runs into the inlet and when the extrusion piston moves away from the suspended piston, low-pressure is produced in the oil chamber. As a result of this, oil moves into the oil chamber after the closing clip moves away from the inlet. When the extrusion piston moves towards the suspended piston; the closing clip closes the inlet, after which the piston starts to press the oil against the suspended piston. Due to the pressure of the compressed oil, the suspended piston moves backwards on the spring enough to allow the oil to drain from the outlet. In idle run, air discharges in a corresponding manner. When the suspended piston moves away from the outlet, oil starts immediately to run from the oil chamber, pressure in the oil chamber decreases and the suspended piston returns back to its starting position and, at the same time, closes the outlet. The thrust force generated by the spring responds to the thrust force of the extrusion piston and the oil chamber empties. The closed outlet prevents the oil from returning back to the pump. This also produces the necessary discharge pressure required in pumping heavier oils. The torsional force of the motor should be measured so that it exceeds the low-pressure generated in the oil chamber. If the low-pressure caused by the extrusion piston moving backwards is proven to be too high in proportion to the torsional force of the motor, the low-pressure, can partly be decreased by narrowing the tip of the closing clip so that it is narrower towards the tip than at the root close to the extrusion piston. This way, the shape of the closing clip prevents the low-pressure in the oil chamber from becoming too high. Such a situation may occur when the oil chamber is large in proportion to the inlet. The extrusion piston and the suspended piston must not touch when the pump runs idle. A hydraulic or electric motor, for instance, can be used to generate the torsional force. The manufacturing material of the pump can vary as long as its composition meets the necessary requirements. The solution of the invention can be varied in a manner obvious to a person skilled in the art, for instance in such a manner that the outlet and inlet need not be round and the pistons can have gaskets in them. Other details, too, can be changed while remaining within the scope of the apparatus defined by the claims.